There is known an electromagnetic flowmeter capable of measuring the flow rate of a fluid flowing through flow passages of various shapes such as an annular flow passage. As such an electromagnetic flowmeter, there is available a technique disclosed in Japanese Patent Application Laid-Open Publication No. 2007.47071 (Patent Document 1). In the technique disclosed in Patent Document 1, both magnetic poles of a magnetic field generator are arranged on one side of the outer wall of an annular flow passage.
More specifically, in the technique disclosed in Patent Document 1, there are provided an excitation device for forming a magnetic field perpendicular to a pipeline outer wall and a pair of electrodes for measuring an electromotive force generated when an electric conductive fluid crosses the magnetic field, and the pair of electrodes and both magnetic poles of the excitation device are arranged only on one side of the pipeline outer wall.
In the above technique disclosed in Patent Document 1, the pair of electrodes and both magnetic poles of the excitation device are arranged only on one side of the pipeline outer wall, so that the flow rate of a fluid flowing through a small (small-diameter) annular flow passage can be measured, while a number of flowmeters need to be provided on the pipeline outer wall in order to measure a fluid flowing through a large (large-diameter) annular flow passage.
In this case, the larger the size of the annular flow passage of the actual equipment, the larger the size of facility for calibration becomes, resulting in an increase of cost.
The present invention has been made in view of the above situation, and an object thereof is to provide an electromagnetic flow rate measurement system capable of performing calibration even for a large annular flow passage by means of a small-scale calibrator and the calibrator therefor.